Olfactory transduction is the process by which olfactory sensory neurons (OSNs) transform odor information into neuronal electrical signals. Over the past two and a half decades, extensive investigations have led to the elucidation of a core transduction pathway in vertebrate OSNs. However, the processes that regulate transduction to allow for proper sensitivity and response kinetics are not well understood. Calcium is a key olfactory transduction regulator. Calcium enters the sensory cilium through the olfactory cyclic nucleotide-gated (CNG) channel during the odor response, amplifies OSN depolarization, and also negatively regulating several olfactory transduction components. This negative regulation governs OSN adaptation--a phenomenon manifested as reduced sensitivity upon sustained or repeated stimulation. In this proposal, we propose to take advantage of multiple genetically modified mouse strains that we generated to: 1) investigate the integration of multiple Ca2+-dependent feedback mechanisms in OSN adaptation (Aim 1); and 2) investigate the role of negative regulatory mechanisms, which function in termination and adaptation, in setting OSN sensitivity at rest (Aim 2). Electrophysiological analysis, at the level of intact olfactory epithelium and the isolated single cell level, will be conducted on mice carrying double or triple mutations for calcium-dependent feedback mechanisms (Aim 1) as well as on mice that lack a calcium-dependent feedback mechanism and also lack efficient calcium extrusion (Aim 2). The long-term goal of this proposal is to elucidate the molecular mechanisms underlying olfaction. The proposed investigation will lead to a better understanding of how OSNs encode the intensity and temporal features of odor stimulations by regulating sensitivity and response kinetics. The knowledge gained from the proposed research will enhance our understanding of normal olfactory function and olfactory dysfunctions.